This invention relates to unsymmetrical azo compounds, unsymmetrical hydrazo compounds, processes for preparing these compounds and processes utilizing these compounds, which azo and hydrazo compounds are characterized by having a tertiary carbon atom joined to one of the azo or hydrazo nitrogens.
Symmetrical azo compounds having a tert-carbon atom joined to each azo nitrogen are known:
E. Farenhorst and E. C. Kooyman, Rec. Trav. Chim. 72,993 (1953).
S. F. Nelson and P. D. Barlett, J. Am. Chem. Soc. 88, 137, 143 (1966).
Unsymmetrical azo compounds where a tert-carbon atom is joined to one azo nitrogen are known. Illustrative compounds of this type, none coming within the scope of the invention are given in:
M. C. Chaco and N. Rabjohn, J. Org. Chem. 27, 2765 (1962).
D. C. Iffland, L. Salisbury, and W. R. Schafer, J. Am. Chem. Soc. 83, 747 (1961).
D. Y. Curtin and J. A. Ursprung, J. Org. Chem. 21, 1221 (1956).
C. G. Overberger and A. V. DiGiulio, J. Am. Chem. Soc. 80, 6562 (1958); ibid 81, 2154 (1959).
H. Wieland, et al, Ann. 514, 145 (1934).
The above compounds are in general difficult to prepare, or are so stable that they are not useful as free radical generators or as blowing agents for plastic foams.
2, 2'-AZOBISISOBUTYRONITRILE IS COMMERCIALLY AVAILABLE. This compound has the structure ##STR2## It has many shortcomings. It is a toxic solid. Moreover, the decomposition residue is a highly toxic solid. Thus, it presents a toxic dusting problem when used in commercial operations and extreme precautions are required in its handling. It is not used in many applications for which it is suited because other areas at the manufacturing site cannot tolerate even the remote chance of exposure to such toxic dust. This is especially true when manufacturing goods for the food and drug packaging industries and many other goods for the household consumer. It cannot be used as a blowing agent for the great majority of the plastic foam market due to the high levels of the toxic residue left in the foamed product. It is insoluble in petroleum hydrocarbon solvents and possesses very low or limited solubility in most of the organic common solvents such as aromatic hydrocarbons, dioxane, alcohol, ether and carbon tetrachloride. This insoluble nature eliminates its use for many applications for which it would otherwise be suitable. It presents problems of metering, incorporation, mixing, dispersing, etc. and necessitates the use of a solvent that in many cases is not ideally suited for the particular application.
The new compositions of the present invention eliminate these problems. Most of the new compositions are liquids and are soluble in petroleum hydrocarbon and most of the other common organic solvents. Thus, no dusting, metering, incorporating, mixing, and dispersing problems are encountered in using these new compositions. Also the new compositions and their decomposition residues have chemical structures that suggest that they are, for the most part, significantly less toxic. Preliminary toxicological studies on the new compositions made in Examples I and IV, set out later, and the decomposition residue of the Example I product indicate that they are significantly less toxic than IXA and its decomposition residue. The less toxic nature of the new compositions coupled with their liquid and high solubility properties allows them to be used in many applications where IXA cannot be used.
Unsymmetrical tert-carbon containing hydrazo compounds are known. Illustrative literature showing the prior art types of these compounds is presented:
Thiele, B. 28, 2600.
Angeli, Rome Atti Accad Tincei 26 I, 95 (1917).
Thiele and Strange, Ann 283, 33 (1894). D. Neighbors et al., J. Am. Chem. Soc. 44, 1557 (1922).